1. Field of the Invention
The present invention relates to a track servo control system for use in an optical disk apparatus to control a light spot from an optical head to follow a track on an optical disk, and more particularly, to a track servo control system for speeding-up a pull-in time of a track servo and improving the stability of a servo system.
2. Description of the Related Art
In optical disk apparatuses, each track spacing can be several microns because a light beam is used to read and/or write data. Therefore, due to its large capacity storage, the optical disk units have been attracting increasingly more attention in this field. An optical disk apparatus is provided with a track servo control system for controlling a light beam (light spot) to follow the light beam on a track. The track servo control system utilizes the diffraction of the light beam from a guide groove (pre-groove) in an optical disk media to obtain a track error signal, thereby applying a servo control to make the light spot follow the track (guide-groove). Such a track servo control system is required for a rapid pull-in of a servo control and an improved stability of the servo system. However, the prior art track servo control suffers from a low pull-in speed of the servo control and a low stability when the optical disk apparatus is operated in the seek mode. This will be described in detail later with reference to the drawings.